Re-organize actions - requirements.txt

[eliselavy]

By running preflight following error here:

https://github.com/jdh-observer/69Xry3ztPAk5/actions/runs/11257071573/job/31300432884

As also nbconvert.yml used also the requirements.txt

- name: installing nbconvert & other required libraries
        run: |
          pip install -r requirements.txt
          python -m pip install jupyter nbconvert nbformat notebook==6.4.12 spacy
          python -m spacy download en_core_web_lg